The long relationship between sheep and humans has led to the development of a large number of breeds. This diversity has allowed the species to meet a variety of environmental challenges and cultural needs.

Selection for wool quality has been of primary importance in the evolution of sheep breeds. Humans began using wool about 10,000 years ago, first by collecting the fibers shed by wild sheep. After sheep were domesticated, they were selected to produce larger quantities of wool that did not shed. The lack of shedding meant that all the wool could be harvested at the same time. It also meant that sheep had to be shorn. Today, only the most primitive and unimproved breeds still shed their fleeces.

Wool is a natural, renewable product with a combination of practical and aesthetic characteristics unmatched by synthetic materials. It is strong, durable, elastic, warm, absorbent, and flame resistant. Centuries of selection for wool qualities are reflected in today's extraordinary range of fleece types, textures, and colors. Wool is categorized into four major types: long wool, fine wool, medium wool, and carpet wool. Long wool fleeces are loose and open, and they hang in locks. The fibers grow up to twelve inches per year and have a sheen and strength that is imparted to finished products. At the opposite end of the spectrum are the fine wool breeds that produce tightly crimped fibers of very small diameter. These wools are prized for the manufacture of soft, delicate garments. Medium wool falls between long wool and fine wool, and it is useful for many different purposes. In North America, however, most medium wool breeds have been selected for meat production rather than wool quality, so that relatively few of them produce anything other than generic, white wool that is blended in large lots for processing.

Carpet wool breeds are double coated, with a coarse, long outer coat for protection from rain, snow, and dust, and a medium to fine inner coat that provides insulation. This type of fleece is unsurpassed for the manufacture of rugs because of its durability. Carpet wool breeds are generally adapted to extreme environments, and the characteristics of the wool are part of that adaptation.

In contrast to the wool sheep just described, "hair sheep" breeds are adapted to hot, humid climates. They lack wool altogether and are covered instead by short hair that is shed annually.

Sheep resources in the United States include all four wool types as well as hair sheep. British breeds have been the primary genetic foundation for the American sheep industry, though breeds from Spain, France, other European countries, and Australia have also been significant. While wool production was historically the primary force in sheep breed development around the world, selection for meat has been of greatest importance in the United States. Sheep dairying has been largely ignored in this country in the past, though interest is increasing.

Spanish explorers and colonists brought the first sheep to the Americas, beginning about 500 years ago. Two remnant populations of these Spanish stocks survive in the United States: the Gulf Coast Native of the Southeast and the Navajo-Churro of the Southwest. English breeds, including the Leicester Long wool and Southdown, were introduced about 1800, along with the Tunis from North Africa. The Spanish Merino, Saxon Merino, and French Rambouillet (a French Merino) were imported beginning in the early 1800s, along with the Cotswold, Cheviot, and several other English breeds. During the middle to late 1800s came the importation of the Dorset, Hampshire, and Suffolk, also from England. Breed imports since 1900 have included the Corriedale from Australia, the Romney from England, the Karakul from the Middle East, and the Barbados and St. Croix hair sheep from the Caribbean. Recent introductions of the Finn sheep from Finland, the Dorper from South Africa, and European dairy breeds have also added to the genetic diversity of the American sheep population.

Despite this genetic breadth, the diversity of sheep breeds in the United States has been neither recognized nor utilized. According to The Livestock Conservancy's Taking Stock: The North American Livestock Census, one breed, the Suffolk, accounts for almost 40% of purebred registrations each year. The top four breeds (Suffolk, Dorset, Hampshire, and Rambouillet) account for about 75%. The remaining 25% of sheep registered each year come from 42 other breeds.

Niche production, especially the specialty wool market, has been essential to the survival of rare breeds of sheep. Handspinners and other fiber artisans have a vested interest in diversity and have played a significant role in the conservation of dual-purpose and wool breeds. The use of sheep in sustainable agriculture should increase interest in rare meat breeds, especially those whose parasite and disease resistance, climate adaptation, maternal ability, nonseasonal reproduction, and other characteristics have obvious economic value. It is important that such opportunities be grasped, for without greater use of sheep breed diversity, it will be lost.

Excerpted from A Rare Breeds Album of American Livestock (out of print), pg 85-86.